The goal of this project is to develop techniques which will permit the structures of complex systems to be predicted or rationalized in terms of known structures of simpler systems. The actual biological systems under study include tRNA, microtubule protein and protein inhibitors of serine esterases. Techniques currently in use include optical activity, fluorescence, affinity labeling and crosslinking. A number of questions currently under examination are probes for flexibility of single strand nucleic acid regions, the role of GTP in microtubule assembly, structural studies on a ternary complex of blackeyed pea trypsin inhibitor with trypsin and chymotrypsin, and the characterization of potential nucleic acid-protein photo-induced crosslinkers.